The invention is based on a priority application EP 04292136.1 which is hereby incorporated by reference.
The invention relates to a method for the reflectometric testing of an optical transmission line, in which a test signal is fed into the transmission line from the direction of an optical transmission device and the reflected signal is analysed. The invention further relates to an optical device for the reflectometric testing of an optical transmission line, having transmission means for feeding a test signal into the transmission line from the direction of the optical device, and having reception means for analysing the signal reflected back to the optical transmission and reception device. The invention further relates to an optical transmission and reception device.
Glass fibres are nowadays being used more and more in so-called metro networks and in access networks. In this context, there is an increasing need for continuous or at least regular monitoring of these optical data connections. The monitoring facilitates preventive measures when a data connection is gradually deteriorating, if this is detected early. High availability of the network is thereby ensured. This is important, for example, for the provision of critical services to business customers. In the event of failures as well, a monitoring device makes it possible to locate the error rapidly and determine the cause of error, in order to allow repair or rectification.
The network operator needs to be able to rapidly find the cause of a connection problem, for example in order to be able to distinguish between trouble with the glass fibre network and trouble at a network node, and, in the event of a glass fibre problem, to be able identify the error location and the type of error or a deterioration occurring along the entire connection.
It is known to use so-called OTDR measuring equipment (OTDR=Optical Time Domain Reflectometry) in order to monitor the quality of optical connections, for instance to identify cable breaks, to find errors, to recognise falling signal levels or the deterioration of properties. Measurements can thereby be carried out as required, for instance in order to document a glass fibre network, or with a special measuring wavelength in multiplex operation in parallel with the working network.
The costs of such measuring equipment are high, because they need to be very reliable and also flexible in order to satisfy all the requirements during operation in a very wide variety of network configurations.
The invention offers assistance for this by a method for the reflectometric testing of an optical transmission line, in which a test signal is fed into the transmission line from the direction of an optical transmission device and the reflected signal is analysed, wherein the transmission device provided for transmitting the useful signal is also used as the transmitter of the test signal by switching it from transmission mode to test mode, and in that the transmission device itself is used as the receiver of the reflected signal.
The invention further relates to an optical device for the reflectometric testing of an optical transmission line, having transmission means for feeding a test signal into the transmission line from the direction of the optical device, and having reception means for analysing the signal reflected back to the optical transmission and reception device, wherein the transmission means is the transmission device provided for transmitting the useful signal, and in that the reception means is the transmission device itself.
The invention further relates to an optical transmission and reception device, that contains an optical device for the reflectometric testing of an optical transmission line, that has transmission means for feeding a test signal into the transmission line from the direction of the optical device, and that has reception means for analysing the signal reflected back to the optical transmission and reception device, wherein the transmission means is the transmission device provided for transmitting the useful signal, and wherein the reception means is the transmission device itself.
The fact that the devices already provided for normal operation are substantially also used for the monitoring device provides very cost-effective monitoring.
Further refinements of the invention can be found in the dependent claims and the following description.